It is well known that piezoelectric materials exhibit a change in their dimensions upon the application of an electric potential thereto. This property has been exploited in numerous prior art constructions to provide electrically controlled moving parts, for effecting motions such as resonant vibrations, small bending deflections, and sharp striking impacts. The possibility has been suggested of constructing a member of an amorphous polymeric piezoelectric material, such as PVDF, and embedding control electrodes in the material for selectively introducing mechanical contractions to control the members. It has also been proposed to construct a moving stage or holder, wherein sets of mutually orthogonal piezoelectric stacks or cylinders are actuated to vary the x, y and z position of an instrument held by the stage.
In various constructions of the foregoing types, the piezoelectric elements may be made of a crystal of high strength and relatively small piezoelectric displacement, or may be formed by sintering or otherwise unifying a mass of piezoelectric grains or powder to achieve a larger member capable of a larger displacement when electrically excited. In the latter case, the elements themselves are generally brittle or friable, and may be vulnerable to environmental degradation from factors such as heat or moisture. Applicant believes that in such larger structures of the prior art, the piezoelectric elements are used for their Property of effecting a gross change in dimensions, and they do not constitute structural members in the sense of having a precise mass, strength and dimensions calculated to achieve load bearing, tensile, bending or stiffness properties This is natural, since the mechanical properties of the most easily worked piezoelectric materials would generally be considered unsuitable for use in structural elements, i.e., as beams or trusses. To employ such materials as add-ons to an independently-designed structural system, however, is inefficient and results in dead weight. There is thus a trade-off between the competing needs for a mechanical structure of low weight and a structure which may be electrically controlled.